During semiconductor processing operations, a wafer may need to be exposed to radiation, plasma discharge, or other phenomena during processing steps such as cure, plasma deposition, photoresist strip, etc. While providing the necessary wafer treatment, the radiation or processing technique may cause large amounts of heat to be transferred to the wafer and the pedestal that supports the wafer. Removing heat flux from the pedestal is often necessary to maintain wafer and pedestal at their desired processing temperatures.
For example, in a UV-cure process, a wafer may be exposed to radiation generated by a mercury vapor lamp. In order to generate said vapor, the lamps must operate at significantly higher temperatures than is desired for processing many films. To accelerate curing as much as possible, it is desirable that the wafer be processed as close to the maximum temperature limit (e.g., around 400° C.) as possible. Typical commercial lamp systems cause the lamp envelope to reach temperatures between 800° and 900° C. The IR radiation emitted by the lamp envelope is incident on the wafer in much the same way as the UV emanating from the lamp discharge. This will cause the wafer temperature to increase above the preferred set-point if active cooling is not performed. Moreover, wafer temperature non-uniformity due to lamp heating (typically 30° C. range) is far worse than that due to pedestal heating (as low as 3° C. range).